Where flash photography is used to capture images of people whose faces are towards the camera, the eyes of the people are often depicted in the images as red regions and sometimes as gold or silver regions. These red/gold/silver regions are types of flash artifact. In low ambient light conditions, when flash photography is desired, human subjects typically have dilated pupils. This means that light from the flash enters the eye through the dilated pupil and reflects from the back of the eye. The amount and type of reflection results in the red, gold or silver color in the captured image. The problem tends to worsen the closer the camera flash is to the optical axis of the camera, and/or as the flash is brighter and these conditions increasingly apply in modern camera phones and other cameras.
Existing approaches involve trying to avoid red eyes occurring in the first place, for example, by using an initial flash before the image is captured in order to provoke the pupils of the human subjects to contract. Once the pupils have contracted less light from the flash is able to enter the eye.
Other existing approaches involve detecting the red/gold/silver eye regions in the captured flash image and making the color of these regions black or dark. However, this often results in an unnatural looking image where the person is depicted as if they have “holes in their eyes”.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known systems for flash artifact removal.